Question

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writing chemical formula & balancing chemical equations - slide 17
four coefficients will help balance this equation. drag the correct coefficients set / combination from the options provided below for balancing the equation and drop it in the box
$\text{pcl}_5 + \text{h}_2\text{o} -----> \text{h}_3\text{po}_4 + \text{hcl}$
4, 1, 2, 1
2, 1, 4, 5
4, 4, 1, 1
1, 4, 1, 5
3, 2, 2, 1
1, 2, 1, 1

Explanation:

Step1: Balance P atoms

There is 1 P on each side, so coefficient of $\text{PCl}_5$ and $\text{H}_3\text{PO}_4$ is 1 initially:
$\text{PCl}_5 + \text{H}_2\text{O}
ightarrow \text{H}_3\text{PO}_4 + \text{HCl}$

Step2: Balance Cl atoms

5 Cl on left, so coefficient of $\text{HCl}$ is 5:
$\text{PCl}_5 + \text{H}_2\text{O}
ightarrow \text{H}_3\text{PO}_4 + 5\text{HCl}$

Step3: Balance H atoms

Total H on right: $3 + 5 = 8$, so coefficient of $\text{H}_2\text{O}$ is $\frac{8}{2}=4$:
$\text{PCl}_5 + 4\text{H}_2\text{O}
ightarrow \text{H}_3\text{PO}_4 + 5\text{HCl}$

Step4: Check O atoms

O on left: $4\times1=4$, O on right: $4$. All atoms balanced.

Answer:

1, 4, 1, 5